For many years it has been recognized that heating of materials within an oven enclosure will be more uniform and rapid if forced circulation of the air within the oven is employed rather than relying on air currents created by temperature differences. Early recognition of this concept is found in U.S. Pat. No. 2,412,103 to Spooner and U.S. Pat. No. 2,957,067 to Skofield.
Most gas and electric ranges used in homes today are not equipped with an air handling device to force an air current. Instead, air circulates within these ovens strictly by means of temperature differences in the oven. These currents may not be uniform within the oven because air is a particularly poor conductor of heat. Such currents may also change as pans and trays are added. Further, these currents cannot exist without certain parts of the oven chamber being hotter than others.
Various patents do exist which disclose ovens with forced air circulation mechanisms built in. Examples include U.S. Pat. No. 3,168,642 to Savio and U.S. Pat. No. 3,812,837 to Tadayoshi. These systems include driving motors disposed outside of the oven interior and are not adapted for use with ovens not so equipped by the original manufacturer.
In the early 1980s, two patents were issued to the assignee of the present invention which relate to portable oven air circulators. These patents are U.S. Pat. No. 4,369,760 and U.S. Pat. No. 4,457,292, both to Jorgenson et al. These patents disclose a portable air circulator for use in cooking ovens which includes a blade, housing, spring motor, gear train and a large flat horizontal oven rack clamp which served as a base for the air circulator. While this design did provide certain positive benefits, the configuration did not provide all of the positive effects of the present invention. First, because the design blew the air across the food rather than down over the food, one side of the food would cook at a faster rate than the other side. Also, the container in which the food was being cooked would often disrupt and interfere with proper air flow reducing the effectiveness of the design. Finally, the housing design shown in these earlier patents reduce the efficiency of the fan in circulating the air.
More recently, U.S. Pat. No. 4,687,908 issued to Kenneth W. Thorn. The Thorn patent discloses a portable fan powered by an electric motor. The convection blower disclosed in Thorn is designed to sit on the floor of the oven between the heating elements and blow the air upwardly. The patent also described means for electrically energizing the motor using the electrical connector of the oven's heating element. This is a high voltage and complicated connection which may present certain safety hazards and difficulties in making the proper connections. The motor only operates to run the blower when the heating element of the electric oven is on. Thus, the design shown in Thorn cannot operate continuously in an electric oven. It also cannot be used in gas ovens. Further, because the device is located on the floor of the oven, it suffers from the problem of blowing air at the bottom of the cookware or bakeware being used rather than blowing air over the food being cooked.
As an improvement over this art, the present invention provides a portable oven air circulator which can be used in both gas and electric ovens to blow air from above down from over the food so as to produce optimal circulation in the cooking oven.